Gels and gel-like materials are widely used for sealing purposes. When under compression gel exhibits excellent sealing properties. A cable splice closure in which gel is used under compression is disclosed in International Patent Application WO 95/15600. In said document, the gel is contained in chambers of the closure housing and is compressed by pressure plates.
It is also known to use gel tapes and to apply gel by winding a gel tape around an object, for example a cable. To apply pressure, another tape may be wound around the gel tape, such as an elastic plastic tape. An example of such a method is disclosed in European Patent Application EP 0 880 212. Alternatively, the gel tape may be compressed by a hard casing constituting an enclosure.
Although the above-mentioned ways of applying and compressing gel provide excellent sealing, they have disadvantages in that additional components (i.e. elastic tape or a hard casing) are required to supply the compression.
It has been proposed to use the combination of a gel layer and a rubber layer for sealing purposes. By providing a rubber layer it is possible to easily compress the gel by slightly stretching the tape when applying it. That is, by tightly wrapping the tape around an object the elastic properties of the rubber are used to enhance the sealing properties of the gel. This synergy of features provides a very advantageous sealing tape.
Chinese Patent Application CN 1 196 558, for example, discloses a sealing tape composed of an elastic insulating layer (rubber layer) with a rough surface, a viscose sealing gel layer on the surface of the elastic insulating layer, and a protecting film on the surface of the gel layer.
A problem that may arise with such tapes is that after being applied, the tape may begin to slide sideways. That is, due to the tensile forces in the rubber layer the tape may move laterally, especially in those regions of the underlying substrate where there is a diameter transition. It will be clear that this lateral movement may cause the seal to be lost as a gap may appear between two successive windings of the tape.